Move fontmgr_bounds labels to tight bounds

The font bounds may be empty, so label the tight bounds instead,
especially since the labels are of the glyph id that touches that edge
of the tight bounds. Also rotate the labels so they dont' run into each
other.

This also fixes SkMetaData::set so that changing an existing value
doesn't cause strange issues with iterators or attempt to use data from
the previous rec after it's been freed. (Found by running viewer in a
asan build.)

Change-Id: Id255beff5d05310f098bd14baf0935e5fd349e7e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/312494
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
3 files changed